New synthetic lubricants



NEW SYNTHETIC LUBRECANTS Delmar L. Cottle, Highland Park, and David W. Young, Westfield, N. 1., assignors to Esso Research and En gineering Company, a corporation of ll slaware No Drawing. Application Getober 29, 1953 Serial No. 389,164

3 Claims. or. zsz -sz This invention relates to new and improved synthetic lubricants. Particularly the invention relates to new compositions of matter that have outstanding lubricating characteristics at both high and low temperatures. More particularly the invention relates to acetals of. glyoxal which are prepared by the condensation of glyoxal with rganic materials containing at least one alcoholic hydroxyl group.

in recent efforts to obtain superior lubricating compositions which have unusual and specific properties, there have been developed entirely new synthetic materials with lubricating properties. in general these new synthetic lubricants are characterized by viscosity properties that are outstanding at both high and low temperatures, especially when compared to mineral oils. These outstanding low and high temperature properties are especially desirable for use in equipment designed to operate over a great temperature differential, such as jet engines for aircraft use, combustion engines for aircraft, and the like. It has been found that mineral lubricating 'oils are generally undesirable for the lubricating of theseengines because of their high and low temperature viscosity limitations.

It has also been found that synthetic lubricants maybe desirable for the lubricating of standard automotive'cngines. In addition to the versatility of their viscosities, the use of some types of the synthetic lubricants investigated have been found to result in very low rates of combustion chamber deposit formation, particularly when used for long periods of time. Low rates of formation of combustion chamber deposits result in increased power factor from fuel, less increase in the octane requirement of the engine, less pre-ignition tendency, and a general overall improvement in engine operation. Also these lubricants may serve to reduce or remove combustion chamber deposits from an engine already heavily loaded with such deposits.

For use in reciprocating engines, particularly as a lubricant for automotive engines, a lubricating composition must meet several requirements. In order to form an effective lubricating film and to maintain that film at low and high temperatures, it must have certain viscosity characteristics. At low temperatures the lubricant must be sufficient labile to how through the circulatory system of the equipment and allow movement of lubricated surfaces Withoutan undue power requirement. Alubricant having an ASTM pour point below about +35 F. has sufiicient low temperature lability to make it satisfactory in these respects for general use. At high temperatures a lubricant must have sufiicient body or thickness to furnish and maintain a satisfactory lubricating film. It has been found that a lubricant that is satisfactory in this respect will have a viscosity at 210 F. of between about 2 and centistokes or 32.8 to 280 Saybolt Seconds Universal. To prevent undue lubricant loss, due to volatility and general molecular disintegration, and to insure against explosion hazards at high temperatures sometimes encountered, a lubricating composition should have a flash point in excess of about 300 F. These requisites are inherent in the term lubricating compositions," as used in'this specification, and the diacetals of this invention are limited to those within these operable ranges. in general the preferred materials, as contemplated herein and as described in the preferred embodiment hereof,

will have an ASTM pour point below about -l5 R, a flash point above about 375 F., and will have a viscosity within the range of 2.6 to 13 centistokes or 35 to 70 Saybolt Seconds Universal at 210 F.

In general it has been found that the above listed properties are a function both of molecular structure and of molecular weight. This fact makes it possible, Within certain limits, to prepare compositions having similar low and high temperature properties in a variety of ways and also enables the manufacturer to tailor a composition to fit a certain setof specifications within rather general limits. H 7

it has now been found, and forms the object of this invention, that compositions having the molecular weight size and configuration necessary for the lubricating characteristics enumerated above may be obtained by condensing organic compounds having at least one hydroxyl group that is alcoholic in nature withglyoxal. When a monohydric alcohol is used as the organic hydroxyl-containing compound, the following reaction takes place.

EXAMPLE l.-?REPARATION OF (CIOHMO)2CH 'CH(0H21C10)2 A. To 8 moles (1264 g.) of C Oxo alcohol was added 60.6 g. dry hydrogen chloride, followed by 193 g. of 30% glyoxal in water (1 mole of glyoxal). Suesequently 200 cc. of C hydrocarbon fraction and g. of p-toluene sulfonic acid were added and water entrained at kettle temperatures of -l01 C. removal of 138 cc. of water, the residue was washed with 10% sodium hydroxide solution and dried over anhydrous potassium carbonate. The dried liquid was stripped at 5 mm. to a liquid temperature of 205 C. The residue has the following properties:

Viscosity at- 210 F SUS 4-6.2 100 F SUS 1233.9 Viscosity index; ASTM pour point F -45 ASTM flash point F 395 It will be noted that the characteristics of this diacetal show it to be a very desirable lubricant.

B. A second preparation of 1,1,2,2-tetraisodecoxyethane was made as follows:

Refluxing a'mixture of 290.3 g. (1.5 moles) of glyoxal (30%), 696 g. (4.4 moles) of C Oxo alcohol, 100 g. of hexane and 5.2 of sodium acid sulfate catalyst at 85 to 115 C. over a period of 7 hours produced 200 cc. of water. The dark red reaction product was washed with two 100 cc. portions of saturated Na CO solution and then two 100 cc. portions of water before filtering and stripping.

The material boiling above 163 C. at 0.25 mm. (kettle at 198 C.) was partially fractionated into the following cuts having the properties given. The yield was 90%.

Cuts, Wt. Percent -11 11-23 23-100 0-i00 Kin. Viscosity, Cs. F.:

210 3. 44 3. 90 5. 85 4. 91 100 19. 58 22. 44 39. 12 30. 53 0 .t 2, 403 1. 706 40 40, 676 3"), 044 Viscosity Index 22 54 100 Pour Point, F 70 60 55 -65 Flash Point, F 455 405 Fire Point, F 515 455 Gravity, API 27. 8 Combustion Test, Total mgs 3. 2 3. 6 Boiling Range, C. 0.25 mm 163-177 177-191 191 163191 Kettle Temperature, C. 0.25

mm 1982l2 212-226 226 198 1 A gm. sample was oxidized in a tared beaker and the total noncombustible material determined.

EXAMPLE 2.--PREPARATION OF 1a 21 )2 27 1a) 2 A mixture consisting of 193.5 (1 mole glyoxal as 30% aqueous solution) of commercial glyoxal, 890 g. (4.4 moles) of C Oxo alcohol, 80 g. of hexane and 4.3 g. of NaI-ISO catalyst was refluxed at 70 to 110 C. for hours during which time 137 cc. of water were collected in the water trap. This reaction product was then washed with three 100 cc. portions of saturated sodium carbonate solution and two 100 cc. portions of water. After filtering to remove traces of water the material was stripped of light ends. The material boiling above 173 C. at 0.15 mm. (kettle at 218 C. at 0.15 mm.) had a dark red color and possessed the following properties. The

yield was 97.5%.

Kin. viscosity, cs. F.:

210 9.34 (56.96 SUS). 100 88.15 (407.2 SUS). 0 11,644.

Viscosity index 88.

Pour point, P 50.

Flash point, F 450.

Fire point, "P 495.

Gravity, API 27.6.

In addition to the simple diacetals illustrated by Examples 1 and 2 above, more complex molecules may be formed using as a connecting link the glyoxal molecule. For instance, a polyhydric compound may be used to link two or more of the hemi-acetals of glyoxal together. An example of these complex diacetals is given in Example 3 below.

EXAMPLE 3.PREPARATION OF COMPLEX DIACETAL OF GLYOXAL Glyoxal (2 m.) l-tripropylene glycol (2 m.).+ j

C 0x0 alcohol (4 m.)

A reaction mixture of 520 g. of C Oxo alcohol, 384 g. of tripropylene glycol, 387 g. of glyoxal (30%), 225 g. of toluene and 13 g. of p-toluenesulfonic acid was refluxed over the temperature range of 94 to 142 C. over a period of 8 hours. The water collected was 260 cc. The reaction product was washed with four 100 cc. portions of saturated sodium carbonate solution and then 150 cc. of sodium chloride, solution. The dissolved water was removed azeotropically. The dry reaction product was then treated with 50 g. animal charcoal at 110 C. for

- 1 hour, filtered and stripped. The yield of material boil- 4 ing above 107 C. at 1 mm. (kettle at 202 C. at 1 mm.) was 74% and had the following properties:

Kin. viscosity, cs. F.

210 9.21 (56.51 SUS). 100 90.60 (418.6 SUS). 0 Viscous.

Viscosity index 81.

Pour point, F ---30.

Flash point, F 410.

Fire point, F 455.

Gravity, API 12.5.

The diacetals of this invention, whether simple or complex, are readily compatible with the various additive materials used in the lubricating art to enhance special characteristics of the lubricant. For example, such materials as viscosity index improvers may readily be blended with these diacetals to thicken them and improve the viscosity-temperature relationship of the oils. Examples of the blending characteristics are given below.

EXAMPLE 4 The 23100% cut of the 1,1,2,2-tetraisodecoxyethane of Part B of Example 1 was blended with 1.0 wt. percent of a polymerized isobutylene having a molecular weight within the range of from about 200,000 to 300,000 Staudinger. The blend was accomplished by heating for one hour at 130-140 C. with stirring. The change in the viscosity characteristics thus obtained are shown EXAMPLE 5.PREPARATION OF 1,1,2,2-TETRA- ISOOCTOXYETHANE AND ITS POLYISOBUTYL- ENE BLEND A mixture of 1086.8 g. (8.35 moles, 10% excess) of C Oxo alcohol, 367.6 g. of 30% glyoxal (1.9 moles glyoxal), 6.8 g. of sodium acid sulfate catalyst and 100 g. hexane was refluxed for 6 /2 hours at -112 C. A total of 250 cc. of water was collected. The mixture was diluted with 200 g. hexane, washed with three cc. portions of 10% sodium carbonate and three 100 cc. portions of water. The material was then distilled under reduced pressure into several fractions. The yield of product was 89%. The 2% polyisobutylene (molecular weight 200,000-300,000 Staudinger) blend of this acetal was made by heating 58.8 g. of acetal with 1.2 g. polyisobutylene at C. for 2 hours.

It will be noted that fractionation beyond the 20% level does not alter appreciably the properties of the acetal. Although the 20-95% cut is somewhat low in viscosity for use as a motor oil per se it can be readily thickenedwith 2% to 2.5% polyisobutylene to give a asaaaea light W. motor oil (specifications for 10 W.: 6000 SUS min. at 0 F.).

As was stated hereinbefore. when a monohydric alcohol is used the synthetic lubricating compositions of this invention conform to the general formula R0 gClL-CHX In the formula X represents --(OR) The Rs of the formula may be alike or different and may be of straight or branched chain configuration, with branched chain structure being'generally preferred. They may contain from about 4 to 30 carbon atoms each, with from 5 to being preferred.

Ordinarily the synthetic lubricants of the invention are prepared by the reaction between glyoxal and organic compounds containingat least one hydroxyl group that is alcoholic in nature. of organic compounds containing at least one alcoholic hydroxyl group that are operable in the concept of this invention is limited by the requirement that the total number of carbon atoms in the diacetal molecule be between about 20 and 130, with from to 100 being especially preferred. In our copending application, Serial No. 323,503, filed December 1, 1952, now Patent No. 2,796,- 423, a partial list of organic compounds containing at least one alcoholic hydroxyl group is given. This list is hereby incorporated and made a part of the instant specification.

Especially preferred, and contemplated in the preferred embodiment of the instant invention are those highly branched chain alcohols prepared by the oxonation of olefin polymers followed by hydrogenation of the resulting oxonated products. This synthesis, known generally as the Oxo synthesis is described in U. S. Patent 2,327,- 066, issued to Roelen in 1943. Briefly, the synthesis involves oxonation of an olefin with carbon monoxide and hydrogen at pressures of about 1000 to 3000 p. s. i. and temperatures in the order of 300 to 400 F. in the presence of a suitable catalyst, usually a heavy metal carbonyl such as cobalt carbonyl. The resulting aldehyde is subsequently hydrogenated to a primary alcohol having one more methylene group than the starting olefin. It is generally preferred to use olefinic polymers as the starting material for the OX0 synthesis, particularly polymers and copolymers of olefins such as propylene, butylene and the like. The Oxo alcohols having from about 8 to 18 carbon atoms, prepared from olefins having from 7 to 17 carbon atoms, are particularly suited for preparing the diacetals of this invention.

Other highly branched chain alcohols such as those prepared by the Guerbet reaction, i. e., the condensation of two moles of an alcohol in the presence of the sodium alkoxide of one of the alcohols, or those highly branched chain alcohols prepared "by aldol condensation may also be used.

When it is desired to prepare a complex diacetal, the polyhydric compound, usually a glycol may be selected from the following partial list of glycols.

Ethylene glycol The propanediols The butanediols Pentanediol Polyalkylene glycols Polyethylene glycols:

Diethylene glycol Triethylene glycol Tetraethylene glycol Polypropylene glycols:

Dipropylene glycol Tripropylene glycol 1,2-cyclohexanediol Decanediol-l,l0

Those glycols of the formula H0 (C H O ll It is to be recognized that the number wherein n is an integer varying from 2 to 12 and x is an integer varying from 1 to 12 are especially desirable.

As was specifically described above, the diacetals of invention are prepared by procedures known to the art. Ordinarily theoretical amounts of the glyoxal and the organic hydroxyl compounds are reacted together in the presence of an acidic catalyst such as hydrogen chloride,

sulfuric acid, sodium acid sulfate, toluene sulfonic acid, etc. The materials are heated until all water has been removed and then purified by percolation through various finely divided solids such as diatomaceous earth or the like. Washing may be accomplished with aqueous solutions containing alkalies such as sodium carbonate, sodium hydroxide, sodium bicarbonate, lime; with acid solutions, with salt solutions containing either alkalies or acids; or with water alone. The washed product may be dried over substances such an anhydrous potassium carbonate, anhydrous calcium chloride or the like, or dried by entrainment of the water with a water-insoluble solvent. The color of the product may be improved by percolation through finely divided solids such as animal charcoal, activated carbon, Attapulgus clay and the like. Finally, the product is stripped of light ends and may, in certain cases, be taken overhead.

As was detailed above, the materials of this invention are readily compatible with viscosity index improvers such as polymerized isobutylene. They may also be blended with various other additive materials such as pour point depressants including maleate/fumarate-vinyl ester copolymers, polymerized acrylate/methacrylate esters and the like. Oxidation inhibitors, detergents, corrosion inhibitors, and other additives for enhancing special characteristics may also be blended with the synthetic lubricants of his invention. Although these materials may be used as lubricants alone, they may also be blended with other lpbricants, either naturally occurring mineral oils, or with other synthetic lubricants, such as formals, silicone polymers, olefin polymers, ethers, ether-esters, glycol ethers, and the like. The liquid synthetic lubricants of this invention may also be converted to solid and semi-solid lubricants by incorporating thickening agents such as the commonly known grease forming soaps, such as the metallic soaps of fatty acids.

To summarize briefly, the instant invention relates to synthetic lubricant compositions which have ASTM pour points below about 35 F., ASTM flash points above about 375 F., and kinematic viscosities within the range of from 2.6 to 13 centistokes at 210 F. a

The total number of carbon atoms in the molecule is preferably from 18 to 125, with 25 to being especially preferred. Specifically contemplated are materials such as 1,l,2,2-tetraisooctoxyethane, 1,1,2,2-tetraisodecoxyethane, l,l,2,2-tetraisotridecoxyethane and the like. Complex diacetals formed from four moles of an alcohol, two moles of glyoxal and two moles of a glycol are also specifically contemplated.

What is claimed is:

1. A synthetic lubricating composition comprising a major proportion of a diacetal lubricating oil having an ASTM pour point below 35 F., a flash point above 375 F., and a kinematic viscosity within the range of 2.6 to 13 centistokes at 210 R, which is selected from the group of diacetals consisting of (l) diacetals having the formula:

(RO) CHCH(OR) wherein R represents branched-chain alkyl radicals containing between about 4 to 30 carbon atoms each and (2) diacetals formed from 4 moles of an aliphatic branched-chain alcohol containing between about 4 to 30 carbon atoms, 2 moles of glyoxal and 2 moles of a glycol of the formula:

HO c n o H wherein n is about 2 to 12, and x is about 1 to 12; the total number of carbon atoms in the molecule being between about 18 and 125, and a minor but viscosity modifying amount of a polymerized isobutylene adapted to modify the viscosity index of a lubricating oil.

2. A composition according to claim 1 wherein said polymerized isobutylene has a molecular weight within the range of about 200,000 to 300,000 Staudinger.

3. A synthetic lubricating composition comprising a major proportion of a lubricating oil having an ASTM pour point below 35 F., a flash point above 375 F, and a kinematic viscosity within the range of 2.6 to 13 centistokes at 210 F., said lubricating oil being a diacetal having the formula:

(RO) CHCH(OR) wherein R represents a branched-chain alkyl group containing between 8 to 18 carbon atoms, and a viscosity V 8 index improving amount of a polymerized isobutylene having a molecular weight within the range of 200,000 to 300,000 Staudinger.

References Cited in the file of this patent UNITED STATES PATENTS 2,360,959 MacDowell et al. Oct. 24, 1944 2,431,008 Wright Nov. 18, 1947 2,460,035 Rogers et al. Jan. 25, 1949 2,499,984 Beavers et al. Mar. 7, 1950 2,512,771 Glavis et al. June 27, 1950 2,668,862 Price Feb. 9, 1954 FOREIGN PATENTS 879,689 France Nov. 30, 1942 

1. A SYNTHETIC LUBRICATING COMPOSITION COMPRISING A MAJOR PROPORTION OF A DIACETAL LUBRICATING OIL HAVING AN ASTM POUR POINT BELOW 35*F., A FLASH POINT ABOVE 375*F., AND A KINEMATIC VISCOSITY WITHIN THE RANGE OF 2.6 TO 13 CENTISTOKES AT 210*F., WHICH IS SELECTED FROM THE GROUP OF DIACETALS CONSISTING OF (1) DIACETALS HAVING THE FORMULA: 